In accordance with standard practice, high pressure pumps such as jet pumps and the like are made with a full metal construction in order to sustain the pressures experienced by the pump. However, a totally metal pump construction does present drawbacks particularly wih respect to corrosion and also with respect to packaging and shipping due to the weight of the metal.
Advances have been made in the construction of pumps through the use of plastic materials alleviating the problems mentioned above. However, the introduction of plastic has brought on a whole new set of problems including heat breakdown which does not occur in a metallic construction.
One example of a plastic pump construction is found in U.S. Pat. No. 3,826,589 issued July 30, 1974 to Starite Industries Inc. According to this patent, a jet pump is formed by a pair of plastic housing sections.
In order to reduce the likelihood of heat related damage to the Starite pump, it includes a metallic shield in the area around the seals at the motor shaft of the pump. This heat shield is designed to keep the heat buildup away from the seals by conducting the heat into the water within the pump chamber of the plastic pump. The heat shield is not designed to carry the heat out of the plastic housing leaving it subject to heat related damage. Furthermore, if the pump looses its prime and the pump chamber is not filled with cooling circulating water, then the pump chamber itself is subject to overheating.